The standard heat of the combustion reaction of liquid n-hexane to form CO₂(g) and H₂O(l), with all reactants and products at 77°F and 1 atm, is ΔH_r = 1:791 × 10⁶ Btu. The heat of vaporization of hexane at 77°F is 13,550 Btu/lb-mole and that of water is 18,934 Btu/lb-mole.

(a) Is the reaction exothermic or endothermic at 77°F? Would you have to heat or cool the reactor to keep the temperature constant? What would the temperature do if the reactor ran adiabatically? What can you infer about the energy required to break the molecular bonds of the reactants and that released when the product bonds form?

(b) Use the given data to calculate ΔH_r (Btu) for the combustion of n-hexane vapor to form CO₂(g) and H₂O(g).

(c) If Q̇ = ΔḢ, at what rate in Btu/s is heat absorbed or released (state which) if 120 lb_m/s of O₂ is consumed in the combustion of hexane vapor, water vapor is the product, and the reactants and products are all at 77°F?

(d) If the reaction were carried out in a real reactor, the actual value of Q̇ would be greater (less negative) than the value calculated in Part (c). Explain why.